Satellites speed up delivery on the Web

Use of the World Wide Web already dubbed ‘the world wide wait’ because of the limitations of the public telephone network could be speeded up using a combination of TV satellite and conventional wired technology. Communications equipment company Rohde & Schwarz says its SpaceMan Internet system provides data access up to 400 kilobits per second […]

Use of the World Wide Web already dubbed ‘the world wide wait’ because of the limitations of the public telephone network could be speeded up using a combination of TV satellite and conventional wired technology.

Communications equipment company Rohde & Schwarz says its SpaceMan Internet system provides data access up to 400 kilobits per second at least five times as fast as the fastest ISDN land lines, with an even better performance over modems.

People who live in remote places without land lines, or those who work on ships, for example, can also use SpaceMan to access the Internet using shortwave radio transmission instead of wired modems.

The problem is simple. Requests to access the Internet are usually short http:theengineer.co.uk, for example and modems are fast enough to deal with these commands.

However, by contrast, the information downloaded is usually relatively large, such as digital maps, databases or software, which causes bottlenecks.

To make multimedia applications that include video more feasible, information from the Internet has to be downloaded much faster. SpaceMan tackles this task by using fast TV satellite transmission to retrieve requested data from the Internet.

This is done via a land-based satellite operations centre in two stages, called the uplink and the downlink.

Satellite transmission is via free channels the so-called transponders of TV satellites such as Astra or Eutelsat. It is based on DVB/MPEG2 digital video broadcasting and picture compression technology.

The Internet user needs a dish to receive satellite signals and a decoder in the form of an extension card installed in the PC.